1. Field of the Invention
The present invention relates to a light-emitting device using a thin film that is made of a luminous material. Further, the present invention relates to electric equipment using the light-emitting device as a display portion or a light source.
2. Description of the Related Art
In recent years, development is proceeding in a light-emitting device (hereinafter referred to as an EL light-emitting device) employing a luminous element (hereinafter referred to as an EL element) that uses a thin film (hereinafter referred to as an EL film) made of a luminous material that provides EL (Electro Luminescence). The EL device is called a light emitting device or a light emitting diode or OLED (Organic Light Emission Diode). The EL (electroluminescent) devices referred to in this specification include triplet based light emission devices and/or singlet-based light emission devices, for example. The EL light-emitting device has an EL element that is composed of an anode, a cathode, and an EL film sandwiched therebetween. The emission of light can be attained from the EL light-emitting device by applying a voltage between the anode and the cathode. In particular, an organic film that is used as the EL film is referred to as an organic EL film. Note that a luminous material in which EL can be obtained includes a luminous material that luminesces via a singlet excitation and a luminous material that luminesces via a triplet excitation.
A metal that has a small work function (typically a metal belonging to Group 1 or Group 2 of the periodic table) is mostly used as the cathode, and a transparent oxide conductive film such as a compound film of indium oxide and tin oxide (ITO) is mostly used as the anode. Therefore, the emission of light attained is visible after the light is transmitted through the anode.
Recently, development is proceeding in an active matrix type EL light-emitting device in which the control of the emission of light by the EL elements provided in respective pixels is through the use of a TFT (thin film transistor), and the development thereof has reached a stage where trial products have been released. All these trial products use a pixel electrode as the anode, and hence the structures thereof are such that the light generated by the EL elements is irradiated to the side of the TFT.
However, because light is no transmitted to the regions where the TFTs and wirings are formed in such structures, a light emitting area (hereinafter referred to as an effect light emitting area) that can actually be seen is reduced drastically. Therefore, the necessity of raising the luminance of the light emitted in order to obtain a bright image leads to the result of hastening the deterioration of the organic EL film.